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What Causes Eczema

What Causes Eczema


Updated June 24, 2014

What Causes Eczema

This person has atopic dermatitis on the arms. Red, scaly plaques can be seen on the inside of the elbows. In adults, atopic dermatitis usually involves the body creases, or flexural areas.

Updated June 24, 2014

What Causes Eczema

Eczema (atopic dermatitis) is a chronic, recurrent skin disease which commonly occurs in infancy and early childhood but can continue or start in adults. Like other allergies and asthma, atopic dermatitis tends to run in families.

It is important to note that atopic dermatitis is not a rash that itches. Rather, it is an itch, that when scratched, results in a rash. Therefore, if the itching can be controlled, and there is no scratching, there will be no rash (eczema).

Atopic dermatitis is very common in childhood, affecting up to 20% of kids, usually before the age of 5. The disease is less common in adults, affecting only 1 to 3% of the population, although can start at any age. It is rare to see atopic dermatitis in adults over 50 years of age.

In general, when atopic dermatitis occurs in infants, it usually is more severe, although many cases resolve or improve in later childhood. Children with atopic dermatitis are much more likely to have other allergic diseases, including allergic rhinitis and asthma.


The diagnosis of atopic dermatitis is made by the history of the symptoms and the examination of the patient by a physician. There is no laboratory test to diagnose this condition.

There are three criteria that must be present in order to diagnose atopic dermatitis:

    1. Atopy. The person must be atopic, or have a family history of allergic diseases in close relatives. There may be rare cases in which a person has atopic dermatitis without evidence of atopy.
    2. Pruritis. Pruritis is the medical term used for itching. The patient must have itching and scratching in order for the rash to occur. If the skin or areas of the rash do not itch or have not been scratched, then the person does not have atopic dermatitis.
    3. Eczema. Eczema refers to the appearance of the rash in patients with atopic dermatitis, and occurs in other skin diseases as well. The rash appears red, with small blisters or bumps present. These may ooze or flake with further scratching. Over the long-term the skin appears thickened and leathery.

Location of Eczema

The location of eczema is dependent on the area of the body that is scratched. In infants and very young children this rash involves the face (especially the cheeks), chest and trunk, back of the scalp and may involve the arms and legs. This distribution reflects where the child is able to scratch, and therefore usually spares the diaper area.

In older children and adults, the location of the rash changes to classically involve the skin in front of the elbows and behind the knees. Eczema can also involve the face (especially the eyelids), and may be limited to the palms of the hands and soles of the feet in certain people.

Triggers for Itching

Itching of the skin can be caused by irritants, infections, allergies and stress. Irritants cause itching through direct stimulation of the skin, and include harsh soaps, chemicals, wool fabrics, heat and sweating. Avoidance of these irritants through use of gentle soaps, wearing cotton clothing, and keeping cool and dry can help prevent itching.

People with atopic dermatitis are more susceptible to skin infections by various bacterial, fungal and viral infections. Many are have large amounts of a common skin bacterium, called Staphylococcus aureus, which can worsen the itching and eczema. Herpes infections (similar to the kind that causes cold sores) and the virus responsible for chicken pox and shingles can cause severe skin infections in people with atopic dermatitis.

Allergies can be a significant trigger for itching in people with atopic dermatitis. Usually allergens that come in direct contact with the skin, such as animal dander and dust mites, cause the most problems, although pollens and mold spores in the air can also worsen the condition.

Food allergies can also be a major trigger for people with atopic dermatitis, particularly in children. Egg and milk allergy are the most common food allergies in children worsening eczema, although other food allergies are also common.

Allergy testing is an important part of the evaluation of patients with atopic dermatitis, and avoidance of these triggers, both environmental and food allergens, can significantly improve the disease.

Find out more about the prevention and treatment of atopic dermatitis.


    1. Atopic Dermatitis Practice Parameters. Ann Allergy Asthma Immunol. 2004;93:S1-21.
    2. Beltrani J. J Allergy Clin Immunol. 1999;104:S87-98.
    3. Sicherer S. J Allergy Clin Immunol. 1999;104:S114-22.

DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.

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